Reference: Advance for Speech-Language Pathologists and Audiologists (Oct. 3, 2011)

Mild Hearing Loss
Linked to brain atrophy in older adults

Declines in hearing ability may accelerate gray matter atrophy in auditory areas of the brain and increase the listening effort necessary for older adults to comprehend speech successfully, a new study has shown.  When a sense is altered, the brain reorganizes and adjusts.  In the case of people with poor hearing, researchers found that the gray matter density of the auditory areas was lower in people with decreased hearing ability, suggesting a link between hearing ability and brain volume.

"As hearing ability declines with age, interventions such as hearing aids should be considered not only to improve hearing but to preserve the  brain," said lead author Jonathan Peelle, PhD, a research associate in the Department of Neurology, Perelman School of Medicine, at the University of Pennsylvania in Philadelphia.  "People hear differently, and those with even moderate hearing l0ss may have to work harder to understand complex sentences."

In a pair of studies, researchers measured the relationship of hearing acuity to the brain, first measuring the response of the brain to increasingly complex sentences and then measuring cortical brain volume in the auditory cortex.

Older adults, ages 60-77, with normal hearing for their age were evaluated to determine whether normal variations in hearing ability impacted the structure or function of the network of brain areas supporting speech comprehension.

The studies found that people with hearing loss showed less brain activity on functional magnetic resonance imaging (fMRI) scans when listening to complex sentences. People with poorer hearing also had less gray matter in the auditory cortex, suggesting that areas of the brain related to auditory processing may show accelerated atrophy when hearing ability declines.

In general, research suggests that hearing sensitivity has cascading consequences for the neural processes supporting both perception and cognition.  Although the research was conducted in older adults, the findings have implications for younger adults, including those concerned about listening to music at loud volumes.

"Your hearing ability directly affects how the brain processes sounds, including speech," said Dr. Peelle.  "Preserving your hearing doesn't only protect your ears but also helps your brain perform at its best."

Audiologists should monitor hearing in patients as they age, noting that individuals who still fall within normal hearing ability may have increasing complaints of speech comprehension issues.

Grants from the National Institutes of Health funded the research.

Peele, J.E., Troiani, V., Grossman, M., et al. (2011).  Hering loss in older adults affects neural systems supporting speech comprehension.  The Journal of Neuroscience, 31 (35): 12638-43